I'm looking for a function that allows to sum the elements of an array
along a dimension that can be different from the classical ones (rows or
columns).

Let's suppose for example that:

- A is an array with dimensions 2 x 3 x 4
- I want to compute B, a 2 x 3 matrix with elements equal to the sum of the
corrensponding elements on each of the 3 strata.

I've tried to use   apply(A,3,sum) but the result is a vector, not a matrix.
Another solution is a less elegant

B=matrix(rep(0,6),ncol=3)
for(t in 1:4) B = B + A[ , , t]

May anybody help?
S

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Simone Salvadei

Faculty of Economics
Department of Financial and Economic Studies and Quantitative Methods
University of Rome Tor Vergata
e-mail: simone.salvadei@uniroma2.it <federico.belotti@uniroma2.it>
url: http://www.economia.uniroma2.it/phd/econometricsempiricaleconomics/
<http://www.econometrics.it/>
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